ABCNews -- Last year Americans spent $22.5 billion on dietary supplements, taking everything from a standard multivitamin to fish oil for the heart to magnesium for healthy bones. But how do we know which vitamin pills we need and which we don't? And at what doses do the risks outweigh the benefits? Dr. Eric Rimm at the Harvard School of Public Health sat down with ABC's Medical Editor Dr. Tim Johnson to discuss some of the more talked about vitamins, how much of them we should be taking and whether too much can be detrimental to our health. In a field filled with controversy, most nutrition experts agree on one thing: food, not pills, is still the best way to get essential micronutrients. Our bodies seem to process the vitamins in food better. And...